1. Field of the Invention
The present invention relates to a suspension system, and more particularly to a front suspension system for an electric wheelchair.
2. Description of the Prior Art
A suspension system generally comprises a shock absorbing device and links and used to reduce the bounce or impact to the vehicle caused by a bumpy road, so as to keep the passengers comfortable.
FIG. 1 shows a frame structure of an electric wheelchair, wherein the frame structure 10 essentially includes a main frame 11, and two front wheel retainers 12 and two rear wheel retainers 13 which are disposed at two sides of the front and rear ends of the main frame 11, respectively, to fix the front and rear wheels 14, 15. The front suspension system of the frame structure 10 includes the front wheel retainers 12, and a spring 16 disposed on each of the front wheel retainers 12. With the elasticity of the spring 16, the front wheel retainers 12 can move up and down along with the front wheels 14 to absorb the bounce caused by bumpy road. When the wheelchair moves a flat and smooth or a little bumpy road, the direction in which the front wheel retainers 12 presses the springs 16 is the same as the direction that the springs 16 are compressed, the springs 16 can play the best role in damping and shock absorbing.
When moving on a very bumpy road, the front wheels 14 bounce up and down and cause movement of the front wheel retainers 12, the front wheel retainers 12 will press against the springs 16 in an inclined manner. Therefore, the front wheel retainers 12 press in a lateral direction against the springs 16, namely, the direction in which the front wheel retainers 12 apply the press force is different from the direction that the springs 16 are compressed, which will cause bending of the springs 16, and the damping effect is adversely affected. Besides, the more bumpy the road is, the greater the upward pressing force applied to the front wheel retainers 12 will be. When the upward pressing force applied to the front wheel retainers 12 is great, and the elastic force of the springs 16 is the only force to counteract the upward pressing force, once the elastic force of the springs 16 is not great enough to counteract the upward pressing force, the frame structure 10 of the wheelchair will tip backward, and the wheelchair can't be able to move safely on the bumpy road.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.